Fieldwatch README

The project's README from github.com/OffGridPete/Fieldwatch. As one markdown file: README.md.

Fieldwatch

I built Fieldwatch as a personal tool to look at what Wi-Fi access points and Bluetooth LE ads my phone was able to pick up, so that I could better understand what devices were being used around me. It’s passive, it only listens, there’s no dongle, no account, and no backend server. I wanted something that would work offline in the field.

My goals were to have a modern interface that was easy to use, flexible in how information was displayed so I could customize a view based on what I was trying to do, a filtering engine so I do not have to look at everything, an extensible signature library so I can identify as many radio sources as possible and add new ones on the fly, as well as create reports of what was seen.

I have been using it and iterating on it for a while now, and it has been useful enough that I thought I would share it.

This is a hobby — something I do for fun in my spare time. There is no Fieldwatch backend. There are no ads. Everything lives on the phone. Source and sideload files are in this repository (dist/ for the APK, instruction card, and manual).

It was Spectre through 1.2.14. I later learned that name was already in use by another app, so I renamed this one Fieldwatch to keep the two from being mixed up. Same field tool, new application id (app.fieldwatch), MIT License. Installing Fieldwatch does not replace Spectre on a phone; it is a separate app.

If you spot an error, something stupid, or have a feature idea — in the app or the documentation — please open an issue on this repository. This is how we make it better. I hope you find it as useful as I have. I look forward to hearing how it goes.

Just want to install it? Download Fieldwatch.apk. Instruction card and manual: instruction.txt, Fieldwatch_User_Manual.pdf. What’s new is the changelog for each build. Leave the APK named Fieldwatch.apk. GitHub may say the file is too big to preview — that is their viewer; use Download.

Safety & disclaimer

This is a hobby project, provided as-is under the MIT License. A few things to know before you do:

Put it on a phone

On a phone, the install files are in dist/, not the root of the repo:

Do not rename the APK. Open Fieldwatch.apk from Files (or My Files). Allow install from that app if Android asks.

File What it is
dist/Fieldwatch.apk Sideload APK
dist/fieldwatch-signatures.json Stock catalog for 1.1.11 GitHub update (catalog 77)
dist/fieldwatch-signatures-v2.json Stock catalog for 1.1.12+ GitHub update
dist/instruction.txt Permissions, first launch
dist/Fieldwatch_User_Manual.pdf User manual
CHANGELOG.md What’s new in each build
LICENSE MIT License
NOTICE Third-party attribution

Android 10+. Allow install from the app you used to open the APK. Play Protect may warn that it is not from Play — expected. Full steps are in instruction.txt.

adb install -r dist/Fieldwatch.apk

Upgrading from 1.0.4 or earlier — Fieldwatch now has a real publisher certificate (one-time reinstall)

This release is a little more professional about how the APK is signed. Android attaches a certificate to every app so the phone can tell “this update is from the same publisher as the app I already have.” Through 1.0.4, Fieldwatch used the generic Android developer certificate that the build tools ship with. That is normal while you are iterating, but people who scan a sideload APK (and some scanners) flag it: a public build should not look like a debug leftover. 1.0.5 is signed with an Off Grid Pete LLC certificate instead. Same hobby app; the file now has a publisher name scanners can check. The fingerprint is in instruction.txt if you want to compare.

The catch is one-time. The phone treats a new certificate as a different publisher, so it will not install 1.0.5 on top of 1.0.4 or earlier. You uninstall the old Fieldwatch, then install this APK. After that, later versions use the same certificate, so ordinary updates work again. You will not have to uninstall for 1.1.17.

Uninstall wipes what is on the phone. If you added signatures, changed Settings, named radios, or saved filter presets, do this first: Settings → Export signatures and Export settings. Share or save those two files somewhere you can get them after. They are not the log and not GPS. Then uninstall (long-press the Fieldwatch icon, or adb uninstall app.fieldwatch), install 1.0.5, open it, tap through the disclaimer, and use Import signatures and Import settings. If you never customized, skip the export and just uninstall, then install.

What Fieldwatch is not

Copyright (c) 2026 Off Grid Pete LLC.

Fieldwatch source is licensed under the MIT License. AndroidX, Kotlin, and related libraries remain Apache-2.0. IEEE and Bluetooth SIG assigned-number tables in radiodb.bin are subject to those organizations’ terms. See NOTICE.

Fieldwatch (OffGridPete/Fieldwatch)

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3.9K ·GitHub
Fieldwatch
What is this?Fieldwatch is a receive-only Android app that passively listens for nearby Wi-Fi access points and Bluetooth LE advertisements, so you can see what wireless devices are around you.
Is this an app or a library?It is a standalone Android app distributed as a sideload APK, not a library or framework.
How do I install it on my phone?Download Fieldwatch.apk from the dist/ folder (not the repo root), open it from Files, and allow install from that app when Android asks.
Do I need any accounts, dongles, or a backend server to use it?No — it needs nothing but the phone's own Wi-Fi/Bluetooth radios; there's no dongle, no account, and no backend server.
Will it always detect nearby devices and trackers?No guarantee — radios that are off, cellular-only, asleep, randomized, quiet, or outside what the phone's OS exposes won't show up, and results depend on the handset's own radios, firmware, and OEM battery policies.
What Android version does it need?Android 10 or newer; Play Protect may warn the APK isn't from the Play Store, which is expected for a sideloaded app.
Where does my scan data and location go?Everything stays on the phone — there's no Fieldwatch server, and logged stamps remain local until you explicitly export or share them.
What can it detect versus what can't it see?It picks up Wi-Fi access points and Bluetooth LE advertisements, but explicitly does not do Wi-Fi client/monitor-mode sniffing, Bluetooth Classic inquiry (so HC-05/HC-06 modules won't appear), cellular signals, or direction finding.
What is the 'Moving with you' / possible tail feature?It's a GPS co-travel pattern match that flags a radio seen moving alongside you across locations — the README stresses this is a hypothesis, not proof of tracking or a legal finding.
If I'm upgrading from an old version, what should I watch out for?Versions through 1.0.4 used a generic debug certificate; 1.0.5+ uses a real publisher certificate, so you must export your signatures/settings, uninstall the old app, and reinstall once — after that normal updates work fine.
Why did the author rename it from Spectre to Fieldwatch?The original name 'Spectre' was already used by another app, so the developer renamed it to Fieldwatch with a new application id (app.fieldwatch) to avoid confusion; it does not replace or conflict with the old Spectre app.
What are similar projects?mlmvpn_android, OhMyKeymint, Vela, vivi-music, zhoop, LocationSpoofer, bitchat, hilight-studio
Which topics is it in?bluetooth-le, surveillance, wifi-security, mobile-security, tracking, bluetooth, network-security, osint, privacy-tools, offline-first, android-app, kotlin
Creator
OffGridPete
Size
148.2 MB
Stars
3.9K
Updated
CommitOct 12Releasev1.1.26Oct 12
Age
1mo
Commits · 90 Days